Acoustical substrates are used in a variety of noise reduction applications inside a building structure to create sound controlled room environments. The substrates may be formed into acoustical panels that can be applied to the walls, ceilings (in some instances forming a suspended ceiling system), and acoustical sound treatments or canopies. Acoustical panels with a high noise reduction coefficient (NRC) as established by testing standards such as ASTM C423 (reverberation room method) or ASTM C384 (impedance tube method) are desirable. The NRC provides a relative measure of the percentage of sound that an acoustical structure will absorb versus reflect. An NRC value equal to or greater than 0.65 to 1.0 is generally considered a high NRC, which ideally indicates that more of sound incident on the panel will be absorbed than reflected back to the room. These acoustical panels are preferably self-supporting; however, such acoustical panels may sometimes be heavy and complex constructions to achieve a high NRC value. The sound absorbing materials may then require a heavy perimeter frame, or interior support splines, which adds cost and weight. This may require an extensive structural support system for mounting the panels, increases installed costs, and may limit application and practical panel sizes.
Improved acoustical substrates that are light in weight and exhibit high NRC are desirable.